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Ask HN: What scientific phenomenon do you wish someone would explain better?

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Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#641

Post by perilunar »

Buttons840 wrote: post #497

Flight. How can a plane fly when it's thrust to weight ratio is less than one? It's like, if you can produce 10 pounds of thrust, who would look at that and say "ah ha, we can use this to keep a 100 pound machine miles in the air indefinitely"? I understand flight from a mathematical point of view. I've actually read a few books on the subject, and I could explain how flight works to someone. However, I'm still fishi…

Think of it like a wedge. 10 pounds force on the back of a wedge can easily cause 100 pounds force perpendicular to it.

But there is a tradeoff between force and displacement. Larger force = smaller displacement.

Same with a wing. The thrust force is lower than the lift force, but the horizontal displacement (velocity) of the wing is much greater than the vertical displacement (velocity) of the deflected air.

i.e. small force x large velocity = large force x small velocity

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#642

Post by OkayPhysicist »

ur-whale wrote: post #548

Why does quantum mechanics need complex numbers ? Every time I read an introductory QM book / article, the complex numbers just come out of nowhere and no one bothers to explain how that makes any kind of physical sense.

Imaginary numbers, pretty much everywhere in physics, represent an extra dimension. e^ix results in a unit vector spinning around.

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#643

Post by [deleted] »

Thriptic wrote: post #467
Denzel wrote: post #391

Earlier quoted context omitted.

I was shoulder deep in primary source material (#4) on real-time fuzzy search and wasn’t able to make heads or tails of where everything fit. Until I found a #3 overview that referenced most of the primary sources and put them in context. That paper was worth its weight in gold! Do you have any tips for how to quickly find these #3 materials in other spaces?

The name for what you and the parent described is a review paper. I can't speak for Math or CS, but in life sciences the following techniques would work: 1. Search X and sort by citation count. High quality review papers get cited A LOT, typically in introduction sections of primary research papers. Alternatively, google "[X] review" or "best review paper on X". 2. Look for review journals. Many fields will have jour…

[deleted]

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#644

Post by texasbigdata »

rsp1984 wrote: post #603

Macroeconomics. Central banks are "creating" a trillion here, a trillion there, like nobody's business. But what are the consequences? What is the thought process that central bankers have gone through to make these decisions? Also why, exactly, are they buying the exact assets that they are buying (govt. debt, high-yield bonds, etc..) and why not others (e.g. stocks or put money into startups)? And then, what happen…

America Inc, which dated, by I believe Mary Meeker has one view showing USA on a "GAAP" basis. It's not pretty. Leverage is too high. Profit margins are negative. "growth" (in this case government receipts) underperforms entitlement spend. Interest is some non-material portion of revenue such as 15% to 20% (caveat, even the most highly leveraged private equity bought companies don't spend more than 25% of revenue of amortization and interest, generally speaking).

A better but harder resource is I believe by Piketty (the inequality guy): from balance sheet recessions there's usually only a few ways out. He and his co-authors go through every single knkwn recession in every single country (obviously biased towards recent and Western). What I took away from it is that without population growth the US needs hyperinflation, to default on its debt, or to increase tax revenue's sharply and/or decrease entitlements sharpy. It's up to you to guess which one of those three is most likely.

But the budgetary situation is not tenable.

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#646

Post by habosa »

rsp1984 wrote: post #603

Macroeconomics. Central banks are "creating" a trillion here, a trillion there, like nobody's business. But what are the consequences? What is the thought process that central bankers have gone through to make these decisions? Also why, exactly, are they buying the exact assets that they are buying (govt. debt, high-yield bonds, etc..) and why not others (e.g. stocks or put money into startups)? And then, what happen…

I have done plenty of serious reading on economics but as far as an approachable start, I don't think we can do better than this: https://economixcomix.com/

If you or a friend wants a crash course on econ, check it out.

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#647

Post by texasbigdata »

sideshowb wrote: post #633
super_mayo wrote: post #625

Earlier quoted context omitted.

PhD student here. Not expert on all those questions but: > Macroeconomics. Central banks are "creating" a trillion here, a trillion there, like nobody's business. What is the thought process that central bankers have gone through to make these decisions? The general consensus is that central banks should stay passive and keep prices stable. However, in periods of crisis, like the one we live in, the central bank coul…

>> And then, what happens if a debtor pays back its debt? Is that money consequently getting "erased" again ? >Yep, pretty much... I would add that if the system is fractional reserve then it increases the proportion of the bank's reserve allowing more money to be created. So while it's technically true that it's destroyed you could see the next loan as its reincarnation, no..? I didn't go here in my response above b…

There's also a concept of "capital deepening". Basically, while vague, when your monetary supply growth outpaces GDP, which is not hard to do with low single digit GDP growth you have more capital available for "one unit of GDP". Therefore asset prices go up.

At least for non private companies ...asset prices go up....auctions clear at values with maximum leverage...recession....monetary stimulus....repeat.

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#648

Post by dmichulke »

rsp1984 wrote: post #603

Macroeconomics. Central banks are "creating" a trillion here, a trillion there, like nobody's business. But what are the consequences? What is the thought process that central bankers have gone through to make these decisions? Also why, exactly, are they buying the exact assets that they are buying (govt. debt, high-yield bonds, etc..) and why not others (e.g. stocks or put money into startups)? And then, what happen…

One approach is reductio ad absurdum:

If Central Banks can create money without negative effects, then

- why tax people?

- why even work? Can't we just print enough money for everyone and live happily ever after?

I realize these questions are quite provocative and their answering only explains if it will work but not how or when it will fail.

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#649

Post by exabyte »

vijay_nair wrote: post #483

• Magnetism. There are plenty of videos out there calling it the result of a relativistic charge imbalance. But I've never been able to use this point-of-view to practical use cases like understanding how permanent magnets work or how increasing the number of windings in inductors boosts the magnetic field strength. There were more situations I tried to put this POV into use but I can't remember them off the top of m…

re: Wave-Particle duality : Imagine that the "particle" in its natural state is a wave of energy that pervades spacetime. Assume we are interested in forcing it to reveal itself as a localized "particle": the amplitude of the its waveform as a function of space and time will tell you the probability of it revealing itself as such in that location at that time. Note the wave form is complex, so in order to get the actual probability you have to calculate the magnitude.

The idea is that it is in this waveform until you do something to observe it. Observation requires an exchange of energy, i.e., an interaction. This is why there is always uncertainty, because in order to observe something, that which observes has now intimately interacted with the waveform in order to cause its "collapse" into what we consider to be a particle. A particle very well may just be a highly localized energy that we perceive to be "solid"

You can't, for example, try to get a measurement of the location of a photon without putting a measuring device which absorbs the energy of the photon, modifying its wave function and thus the probability of where it will decide to reveal itself at that point in spacetime.

note: I consider energy, fundamentally, to simply be the consequence of fluctuating. The fluctuation of one thing can interact with the fluctuation of another and, minding conservation, transfer "fluctuation". The direction of that transfer of energy relying may be due to the fact that entropy always increases along the arrow of time, i.e., energy likes to spread itself out just as heat goes from high concentration to low concentration.

Re: Ask HN: What scientific phenomenon do you wish someone would explain better?

#650

Post by Viliam1234 »

aazaa wrote: post #236

Sort of meta, but I always shudder when someone says that science has "proven" something. What sets science apart from most other methods of seeking answers is its focus on disproof . Your goal as a scientist is to devise experiments that can disprove a claim about the natural world. This misconception rears its head most prominently in discussions at the intersection between science and public policy. Climate change…

One thing that rubs me the wrong way about this "no proof ever, only disproof" attitude is that it advantages the new hypotheses too much.

Any hypothesis that I invent at this very moment, is from this perspective in the best position a hypothesis can ever be. There is no disproof. There is even no coherent argument against it, because I literally just made it up this second, so no one had enough time to think about it and notice even the obvious flaws. This is the best moment for a hypothesis... and it can only get worse.

I understand that there is always a chance that the new hypothesis could be correct. Whether for good reasons, or even completely accidentally. (Thousand monkeys with typewriters could come up with the correct Theory of Everything.) Yes, it is possible. But...

Imagine that there are two competing hypotheses, let's call them H1 and H2.

Hypothesis H1 was, hundred years ago, just one of many competing options. But when experiment after experiment was done, the competing hypotheses were disproved, and only this one remained. For the following few decades, new experiments were designed specifically with the goal of finding a flaw in H1, but the experimental results were always as H1 has predicted them.

Hypothesis H2 is something I just made up at this very moment. There was not enough time for anyone to even consider it.

A strawman zealot of simplified Popperism could argue that a true scientist should see H1 and H2 as perfectly equal. Neither was disproved yet; and that is all that a true scientist is allowed to say. Maybe later, if one of them is disproved in a proper scientific experiment, the scientist is allowed to praise the remaining one as the only one that wasn't disproved yet. To express any other opinion would be a mockery of science.

Of course, there always is a microscopic chance that H1 might get disproved tomorrow, and that H2 might resist the attempts at falsification. But until that happens, treating both hypotheses as equal is definitely NOT how actual science works. And it is good that it does not.

In actual science, there is something positive you are allowed to say about H1. Something that would make the strawman zealot of simplified Popperism (e.g. an average teenager debating philosophy of science online) scream about "no proof ever, only disproof". The H1 is definitely not an absolute certainty. But there is something admirable about having faced many attempts at falsification, and surviving them.

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